Evaluation of the host specificity of Spathius galinae (Hymenoptera: Braconidae), a larval parasitoid of the emerald ash borer (Coleoptera: Buprestidae) in Northeast Asia

Authors: Duan, Jian; GOULD, JULI - Animal And Plant Health Inspection Service (APHIS); Fuester, Roger

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2015
Publication Date: 6/19/2015
Citation: Duan, J.J., Gould, J.B., Fuester, R.W. 2015. Evaluation of the host specificity of Spathius galinae (Hymenoptera: Braconidae), a larval parasitoid of the emerald ash borer (Coleoptera: Buprestidae) in Northeast Asia. Biological Control. 89:91-97.

Interpretive Summary: Classical biological control involves the introduction and establishment of non-native beneficial insects (i.e, biocontrol agents) such as predators and parasitic wasps, potential risks of the would-be introduced biocontrol agents to non-target organisms need to be assessed prior to environmental release. USDA scientists from the ARS and APHIS evaluated the potential non-target risk of introducing the beneficial wasp (Spathius galinae) from the Russian Far East for biological control of the emerald ash borer in the United States, where it has killed millions of ash trees. Results of the study showed this beneficial wasp is highly specialized to attack emerald ash borer and only attacks one of the 15 tested species of North American non-target insects, which is the gold spotted oak borer and a pest of red oaks in California. These findings provided critical information needed by USDA APHIS to assess the non-target impact of this beneficial wasp prior to the approval for environmental releases in the U.S.

Technical Abstract: Host-specificity determination prior to the introduction of non-native natural enemies (predators and parasitoids) is a critical component of the risk assessment for modern classical biological control programs. In the present study, we assessed the host specificity of a newly described parasitoid, Spathius galinae Belokobylskij & Strazanac, which is native to Northeast Asia, for classical biological control of the invasive emerald ash borer (EAB), Agrilus planipennis Fairmaire, in North America. Along with foreign exploration for natural enemies of EAB in 2010 and 2012, we surveyed ash phloem and/or wood-boring insects and their parasitoid complex from artificially stressed and EAB-infested Oriental ash (Fraxinus rhynchophylla Hance) trees in natural forest stands in Primorskiy Kray (Vladivostok area) of Russia. Once quarantine colonies of S. galinae were established in the U.S., we tested the parasitoid against a list of 15 species or groups of North American wood-boring insects that was selected along a continuum from closely related taxa (e.g., Agrilus spp. in the family Buprestidae in Coleoptera) to distantly related ones in Lepidoptera and Hymenoptera. While three of the tested insects, the longhorned beetle Neoclytus acuminatus, the clearwinged moth Podosesia spp. and the eastern ash bark beetle Hylesinus fraxini attack ash as their main host, the rest attack non-ash trees such as birch, maple and oak. Results from our field survey showed that S. galinae did not attack bark beetles (Hylesinus spp.) and longhorned beetles (unidentified Cerambycidae) that coexisted with EAB on the same infested ash trees in its native range. Additionally, S. galinae did not attack 14 species or groups of non-target wood-boring insects infesting both ash and/or non-ash trees such as (birch, maple or red oak). The only non-target attack was on the gold spotted oak borer, Agrilus auroguttatus Schaeffer, infesting red oak. The rate of parasitism on the gold spotted oak borer was significantly lower than the rate on EAB under laboratory conditions that favored parasitism. These findings indicate that the host specificity of Spathius galinae is highly constrained by the phylogenetic relationship to its co-evolved EAB host and may be restricted at the host genus (Agrilus) level.